Question

How to read and write a float to a binary file in C

Answer 1

#include <stdio.h>
  
int main()
{
    float f = 3.14159f;
    FILE *writep;
  
    writep = fopen("data.bin","wb"); 
    fwrite(&f, sizeof(float), 1, writep);
    fclose(writep);
  
    float tmp = 0.0;
    FILE *readp;
  
    readp = fopen("data.bin","rb");  
    fread(&tmp, sizeof(tmp), 1, readp); 
    fclose(readp);
      
    printf("%f\n", tmp);
     
    return 0;
}
  
  
  
/*
run:
  
3.141590
  
*/
 

 

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Answer 2

#include <stdio.h>

int write() {
    FILE* file = NULL;
    if (fopen_s(&file, "data.bin", "wb") != 0 || file == NULL) {
        perror("Error opening file");
        return 0;
    }

    float number = 3.14f; // Example float value
    fwrite(&number, sizeof(float), 1, file); // Write the float to the file

    fclose(file); // Close the file

    return 1;
}

int read() {
    FILE* file = NULL;
    if (fopen_s(&file, "data.bin", "rb") != 0 || file == NULL) {
        perror("Error opening file");
        return 0;
    }

    float number = 0.0f;
    fread(&number, sizeof(float), 1, file); // Read the float from the file

    printf("Read float: %f\n", number); // Print the float value

    fclose(file); // Close the file

    return 1;
}

int main() {
    if (write() == 1) {
        read();
    }

    return 0;
}



/*
run

Read float: 3.140000

*/

 

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